Filter module and process for manufacture of same

ABSTRACT

The present invention relates to a filter module comprising a body of wound layers of a sheet material, said sheet material having a plurality of openings formed therein, said openings forming two types of channels within the wound layers of sheet material of said body, said channels extending in a direction from the inner peripheral surface to the outer peripheral surface, a first type of channels being open at one end at said outer peripheral surface of the body and closed at the other end located adjacent to said inner peripheral surface, a second type of channels being open at one end at said inner peripheral surface of the body, and closed at the other end located adjacent to said outer peripheral surface, said channels of the one type being separated from the channels of the other type by portions of sheet material, wherein the sheet material has areas at the edge of the openings forming the inlet channels the thickness of which being smaller than the thickness of the sheet material remote from those openings, as well as to a process for the manufacturing of such a filter module.

The present invention relates to a filter module and a process formanufacture of same.

The filter module according to the present invention comprises a body ofwound layers of a sheet material, said body having an inner and an outerperipheral surface, a winding axis and a passage extending along thewinding access of said body and in fluid communication with said innerperipheral surface. The sheet material has a plurality of openingsformed therein, said openings forming at least two types of channelswithin the wound layers of sheet material of said body, said channelsextending in a direction from the inner peripheral surface to the outerperipheral surface.

A first type of channel formed in said body is open at one end at theouter peripheral surface of the body and closed at the other end locatedadjacent to the inner peripheral surface. A second type of channel isopen at one end at the inner peripheral surface of the body and in fluidcommunication with said passage and closed at the other end locatedadjacent to the outer peripheral surface.

The different types of channels are separated from one another byportions of sheet material such that fluid to be filtered and enteringone type of channels may reach the other type of channel and exit thefilter module only by migrating through a portion of said body formed bythe sheet material separating these different types of channels.

One type of channel is communicating with a fluid inlet of said filtermodule. Channels of this type are called in the following inletchannels; another type of channels is communicating with an outlet ofsaid filter module and these channels are called in the following outletchannels.

Filter modules of this type are generally known, for example, from thePCT application WO 03/041829 A2.

Another filter module of this type is known, for example, from U.S. Pat.No. 2,339,703.

While the filter modules as mentioned above provide an interestingapproach to a filter module of filter paper (U.S. Pat. No. 2,339,703)and other filter materials (WO 03/041829), they have been foundineffective in a number of aspects.

The object of the present invention is to provide an improved filtermodule of the above-described type which provides a longer service lifefor the filter modules by simple and cost effective means.

This object is achieved by a filter module according to claim 1.

In its simplest configuration the body of the filter module may have oneinlet and one outlet channel. For practical purposes, in mostapplications, however, the body of the filter module will have both aplurality of inlet and outlet channels.

The following explanations of the present invention refer toconfigurations with a plurality of channels. However, these explanationswill mostly apply also to the afore-mentioned simplest configuration.

According to a first aspect of the present invention, the filter moduleis manufactured from a sheet material which has areas at the edge of theopenings forming the inlet channels, the thickness of which beingreduced to a predefined smaller thickness than that of the sheetmaterial remote from those openings.

Such structure of the sheet material in the vicinity of the openingsforming the inlet channels increases the surface area on the inletchannel side, a means which enhances the filtration capacity of thefilter module thereby increasing the service life of the filter module.

Thus, the surface area provided by the inlet channels of these wrap rollfilter modules is no longer a limiting factor for the filter area andcapacity of the filter module, while the surface area provided by theoutlet channels, i.e., down-stream of the filtration module, usuallynever was limiting the service life of the filter modules.

This effect may already be achieved with a relatively small reduction inthe thickness of the sheet material as long as the gap created in theseareas in between the layers is significantly larger than the largestaspect of the particles contained in the fluid to be treated.

The areas of sheet material of smaller thickness at the edge of theopenings forming the inlet channels preferably are deformed, morepreferably compressed to a predefined thickness.

While in principle various operations could be used in order to reducethe thickness of the sheet material at the edge of the openings formingthe inlet channels, e.g., by machining operations, deforming thematerial or compression of the material to a predefined thickness ispreferred. This is especially true when a sheet material is used whichis compressible itself.

Preferably, the areas of smaller thickness of the sheet material extendin the direction to openings forming outlet channels. Of course theextension in that direction is only such that the filtration process isnot negatively affected. In doing so it provides a means to optimize thelength of the migration path for the fluid from the inlet area of thefilter module through the body of sheet material to the closest outletchannel.

In a further preferred embodiment of the present invention, the areas ofsmaller thickness extend in the direction of adjacent openings of thesame kind, the areas such forming one or more continuous flow pathsextending along the winding direction of the sheet material.

Such embodiment provides for an optimum of inlet channel surface areaand an optimum of service life for the filter module.

As an alternative to deformation or compression of the sheet materialprior to winding the same to form the body of the filter module, a firststrip-like element of a macro-porous material may be co-wound with thesheet material to cover the areas of the sheet material comprising theopenings forming inlet channels. By co-winding the macro-porous materialin strip-like form, automatically a compression of the sheet material inthe area comprising the openings forming inlet channels is achieved anddue to the macro-porous character of the material, the surface area ofthe sheet material is still accessible to the fluid to be filteredwithout hindering the fluid essentially to contact the sheet materialsurface on the inlet side of the filter module. Optionally, thestrip-like element may comprise openings essentially matching theopenings of the sheet material.

The term macro-porous as used in this context means anythree-dimensional open-pored structure which does not contributenoticeably to the filtering effect and which preferably essentiallypresents no flow restriction to the fluid in the inlet channels.

Again, an increased surface area on the inlet side of the filter moduleis provided, which makes maximum use of the sheet material used for thewrap roll. In addition, the use of the strip-like element of amacro-porous material provides for a defined and pressure resistantstructure for the filter module and may in addition serve to reinforcethe body of the filter module. Therefore, such type of filter module mayalso be used in heavy duty applications.

While the macro-porous material as an additional material co-wound withthe sheet material results in a compression of the sheet material in thearea of the openings forming the inlet channels already, it is preferredthat the macro-porous material is at least less compressible than thesheet material in order to make sure that the macro-porous structure ofthe strip-like element is maintained in the finished filter module. Morepreferably, the macro-porous material is essentially incompressible.Essentially incompressible means that the macro-porous materialessentially does not change its macro-porous structure upon theapplication of the compression forces needed to manufacture the filtermodule.

In order to make maximum use of the increased surface area on the onehand and in order not to disturb the overall structure of the filtermodule on the other hand, it is preferred that the strip-like elementhas tapering edges or edges with a wedge-shaped cross-section.

In such a configuration the compression of the sheet material is maximalin the area of the openings forming inlet channels, whereas thecompression gradually is reduced in the direction extending from theseopenings in the direction to the outlet channels.

This allows for a smooth building-in of the strip-like element into thefilter module which at the same time provides for additional securitywith respect to avoidance of bypasses between adjacent layers of sheetmaterial.

In order to provide further security with respect to the bypass problem,a second strip-like element may be co-wound with a sheet material tocover the areas of the sheet material comprising the openings formingthe outlet channels. The second strip-like element may be used togetherwith the first strip-like element or independent of the same. The secondstrip-like element provides for a compression of the sheet material inthe area of the outlet channels serving for an intimate contact of thesheet material around the openings forming the outlet channels whichprovides for additional safety against unwanted bypasses.

Preferably, the second strip-like element has openings to essentiallyregister with the openings of the sheet material.

The material from which the second strip-like element is made, may bethe same as the sheet material, since the material from which the secondstrip-like element is made need not necessarily be incompressible. Themain function of the second strip-like element is to provide additionalcompression forces in the areas of the outlet channels so as to providefurther security against bypasses.

The second strip-like element therefore may be made of a depth filtermaterial, but may also be in some applications made of an essentiallynon-porous material. In addition, the second strip-like element may bemade of a material which is essentially incompressible.

As is the case for the first strip-like element, the second strip-likeelement may also preferably have the form of a band having tapering orwedge-shaped cross sectioned edges. As with the first strip-likeelement, also here the wedge-shaped cross section allows for a smoothco-winding of the second strip-like element with the sheet material.Also the compression exerted by the wedge-shaped strip-like element ismaximal at the edges of the openings forming the outlet channels and isgradually reduced in the direction of the edges of said band.

The dimensions of the openings in their smallest aspect should not bebelow about 0.5 mm except for sheet materials which do not swell incontact with the fluid to be filtered. Otherwise an undue increase inpressure drop may be observed. Preferably the smallest aspect is about 1mm or more. In case of round openings this aspect corresponds to thediameter of the openings. The largest aspect of the openings may largelyvary.

It is readily understood that the shape of the openings is not limitedto a round, oval or elliptic form or slot-like shape, but the openingsmay have any polygonal form, e.g., rectangular or square shaped.

According to a further aspect of the present invention it is importantthat a majority of the openings of a layer (or one winding) of sheetmaterial forming the inlet channels incompletely register withcorresponding openings of an adjacent layer of sheet material.

By the specific size, shape and/or arrangement of the openings in thesheet material forming the inlet channels such that the openings of onelayer do only incompletely register with the openings of the adjacentlayer also contributing to the formation of the inlet channels providedin the body, an increased surface area is provided. Surprisingly, suchincompletely registering of the openings may provide for a drasticincrease in surface area, but at the same time, the increase in pressureresistance or pressure drop remains limited to acceptable values.

Incomplete registering of the openings provides a remarkable effect ofincrease in surface area resulting in an increased dirt capacity andtherefore in an increased service life of the filter module when theoverlap of the openings in the average amounts to about 90% or less.Therefore, for applications which are rather sensitive for increase ofpressure resistance on the side of the inlet channels, an overlap of theopening of about 90% in the average may provide for a remarkableadvantage over the wrap rolls disclosed in the prior art.

The overlap percentage mentioned above and below relates an overlap ofareas of sheet material occupied by the respective openings calculatedfor the openings forming the inlet channels of the whole body.

For applications which are less sensitive to pressure resistance orpressure drop, the incomplete registering may correspond to an averageoverlap of the openings of about 80% or less which provides for a stillincreased effect of larger surface area on the inlet channel side.

When the incomplete registering of the openings corresponds to anaverage overlap of less than about 50% the effect of increase in dirtcapacity and service life is no longer as pronounced as in the casesdiscussed above, whereas at the same time the increase of pressureresistance of the inlet channels becomes a factor which may not beneglected anymore.

Therefore, the incomplete registering of the openings preferablycorresponds to an average overlap of about 50% or more.

It is easily understood by the person of ordinary skill in the art thatthe advantageous effect of increase in surface area on the inlet channelside not necessarily requires that essentially all of the openingsforming inlet channels incompletely register with the correspondingopening of the adjacent layer(s). It is, however, preferred that atleast about 75% of the openings (by number) forming the inlet channels,more preferably at least about 85% incompletely register with thecorresponding openings of an adjacent layer. This measure ensures a morehomogeneous increase of inlet channel surface throughout the body.

While the incomplete registering of the openings could be achieved byusing openings of different shape and/or size, it is preferred accordingto the present invention to use the openings for each type of channelsof a substantially uniform size and shape, which greatly facilitates theproduction of the sheet material having the openings formed therein.

This also facilitates the design of the filter module and the tools formanufacturing same.

The afore-discussed teaching of incomplete registering of the openingsforming the inlet channels is in contrast to the teaching of U.S. Pat.No. 2,339,703, which specifically requires that the openings registerwith one another. This reference specifically calls for a suitablespacing of the openings to cause the openings to mate. Anything morethan a slightly irregular positioning of the openings resulting inslightly irregular edges of the channels is not accepted to avoidinterference with the effectiveness of the filter.

The same teaching may be derived from WO 03/041829 A2. This referenceallows an orientation of the channels with respect to the winding axisof 30° to 90°.

According to another aspect of the present invention the openingsforming the channels are preferably separated from one another by staysof sheet material. The stays may be easily designed to provide enoughstability to the body to withstand a substantial pressure differentialduring operation of the filter module.

In a preferred embodiment the openings forming the inlet channels havean extension in the winding direction of the sheet material which islonger than the extension of the stays separating these openings fromone another in the same direction. Such type of design of the sheetmaterial will avoid that stays in between openings may overlay anopening of an adjacent layer of sheet material and disturb the channelstructure.

The structure of the channels, especially of the inlet channels, may beof a simple, more or less tubular form showing projections of recessesin the surface of the channels which result from the incompleteregistering of the openings forming the inlet channels. However, theform of the channels can also be much more complex. In case the openingsof the inlet channels have an extension in the winding direction muchlonger than the extension of the stays measured in the same direction, aplurality of openings may form inlet channels that constitute together acontiguous ring shaped channel structure which is intersected at variousportions by stays separating the openings from one another.

In this case, a relatively large surface area is provided per inletchannel while at the same time, the stays of sheet material intersectingthe channel volume still provide for sufficient stability, not only ofthe structure of the inlet channels during operation of the filtermodule but also facilitate winding of the sheet material to form a bodyin a precise and repeatable manner.

In order to maximize the surface area of the inlet channels versus thesurface area of the outlet channels while keeping consumption of sheetmaterial at a minimum, it is preferred that the number of openingsforming inlet channels is higher than the number of openings formingoutlet channels.

Another measure to promote such an effect is to make the openingsforming the outlet channels smaller than the openings forming the inletchannels.

A significant effect of this measure may be observed when the differencein size of the openings amounts to about 10% or more, based on the sizeof the openings forming the outlet channels.

In order to make maximum use of the sheet material used to produce thewrap roll body, the number of inlet channels is preferably higher thanthe number of outlet channels.

The number of inlet channels may be two fold or more of the number ofoutlet channels.

Calculations done by the present inventors show that when the number ofinlet channels is approximately threefold the number of outlet channels,a maximum use of the sheet material is possible. This maximum use notonly relates to its use to provide a stable filtering structure but alsoto its effect on the filter capacity of the filter module, which meansits service life.

Preferably, the openings in a sheet material for each type of channelsare arranged in parallel rows. This allows an easy design of the sheetmaterial and the arrangement of the various types of channels so as tomake maximum use of the sheet material.

Preferably the openings forming the inlet channels are arranged ingroups of two or more adjacent rows, whereas the openings forming theoutlet channels are arranged in groups of a lesser number of rows. Thenumber of rows in a group of rows of openings forming outlet channelsmay be just one.

This allows an increase of surface area for the inlet channels whilekeeping the surface area of the outlet channels to the minimumnecessary. During filtration the fluid entering the inlet channels willmigrate through the sheet material and be collected in the adjacentoutlet channels.

Maximum use of the sheet material requires that more than one inletchannel provide fluid to be filtered for one outlet channel.

In order to facilitate the incomplete registering of the openings, in apreferred embodiment according to the present invention the openingsforming the inlet channels are arranged in a predefined pattern, eachpattern comprising a number of openings, said pattern being repeatedmultiple times along the length or winding direction of the sheetmaterial such that the distance between openings of the same kind withinone pattern is different from the distance of adjacent openings of thesame kind belonging to two subsequent patterns.

This means that, for example, when a punching tool is used to provide anumber of openings in the sheet material, the punching tool is used withan offset for forming the adjacent opening pattern such that thedistance between adjacent openings formed in two punching operations isdifferent from the distance between adjacent openings resulting from onepunching operation.

According to another aspect of the present invention the design of themodule may be advantageously used to a depth filter characteristic. Tothat effect, the sheet material is selected from a depth filter materialand said sheet material of the module is maintained in a compressedstate, such that the body of wound layers constitutes a depth filterunit precluding bypasses. These measures ensure that the fluid to befiltered migrates through the depth filter material and does not find ashortcut from an inlet to an outlet channel between adjacent layers ofsheet material.

It has been found that a compression of the sheet material, such thatthe thickness of the compiled layers of the body amounts to about 99% orless of the thickness of the same number of individual layers of sheetmaterial, is often enough to solve the bypass problem. The amount ofcompression needed is of course depending on the compressibility of thesheet material itself so that with easily compressible sheet material amore pronounced compression of the body may be advantageous.

The compression of the body within the above mentioned limits issuitable for solving the bypass problem especially where the sheetmaterial used is a material which swells in contact with the fluid to betreated. In such a case, in addition to the compression forces exertedon the sheet material in the dry state of the body, the forces createdin the course of the swelling of the sheet material support providing anintimate contact of the adjacent layers of the sheet material within thebody.

Furthermore, the forces generated upon swelling of the sheet material donot only act in the same direction as the compression forces but also inperpendicular directions thereof which further contributes to minimizethe bypass risks.

The forces created by the swelling of the sheet material do not simplyadd to the compression forces when an elastically/plastically deformablesheet material is used. Part of the forces will then result in a partlypermanent deformation of the microstructure of the depth filtermaterial.

When a sheet material is used which does not swell in contact with thefluid to be filtered the restoring forces of the elastically orelastically/plastically deformable sheet material are solely responsiblefor maintaining the intimate contact of adjacent layers of sheetmaterial. In such cases a somewhat higher compression of the body may beadvisable.

The use of easily compressible sheet material opens up multipleopportunities to modify the filter characteristic of the filter moduleand to adapt the sheet material in the body to various filtration taskswithout having the need to produce different types of sheet material. Byvarying the degree of compression of the body the permeability of thesheet material can be modified, resulting in modified retention andseparation characteristics.

Typical sheet materials of cellulosic fibers have mass per unit area ofabout 300 to about 2.000 g/m² and a thickness of about 2 to about 7 mm,more preferably about 3 to about 6 mm. Sheet materials of cellulosicfibers with a thickness of about 4 to about 5 mm are most preferredbecause they allow a most economic drying process during themanufacturing of the sheets.

However, usually the thickness of the compiled layers of the compressedbody will amount to about 20% or more of the thickness of the samenumber of individual layers of sheet material. If the compression ishigher than that limit, there might result an undesirable high reductionin the dirt retention capacity. On the other hand, a high compressionimproves the filtration efficiency for smaller particles.

A further preferred limit to compress the body corresponds to about 50%or more of the thickness of the compiled individual layers of sheetmaterial. A compression within this limit is easier to be handled withrespect to the desired filter characteristics.

Nevertheless, often enough with compressible sheet material compressionto a thickness of about 85% or more of the compiled individual layerswill provide very good results. In a large number of cases, thecompression preferably amounts to a thickness of the compiled individuallayers of about 97 to about 85%.

In a number of applications, for example in the biopharmaceutical orfood technology area, it is of utmost importance to use materials onlywhich have been certified for the type of application.

In this respect, in a preferred embodiment of the present invention thebody of wound layers essentially consists of a unitary material, whichmeans that the body is essentially constituted by the sheet materialitself not needing any sort of adhesive or other type of auxiliaryagents or means to provide for a bypassfree depth filter material.

Closure of the first type of channels adjacent to the inner peripheralsurface may be accomplished by covering corresponding openings of thesheet material with a fluid impervious material, e.g., a tube elementwhich includes openings to register with the openings of the sheetmaterial of the second type channels and preferably defining thepassage. The tube element may optionally function as a support element.

Likewise, the closure of the second type of channels adjacent the outerperipheral surface of the body may be accomplished by covering therespective ends of the second type of channels with a fluid imperviousmaterial, however, leaving the first type of channels uncovered.

In the alternative, closure of the respective ends of the first andsecond type of channels may be accomplished by non-perforated portionsof one or more further windings of sheet material.

In order to provide safe closure of the channels at one end thereof bysheet material, it is preferred when the innermost and outermost layersof sheet material, respectively, are compressed at least to the extent,the body as a whole is compressed.

This ensures that especially at the end portions of the channels nobypass or leakage may occur and again such measures avoid any use ofadhesive or any other auxiliary material to that effect.

More preferably, at least several, e.g., three innermost and at leastseveral, e.g., three outermost layers are compressed to an extentsubstantially corresponding to the degree of compression of the body asa whole. Of course, even more innermost and/or outermost layers may beused to provide a closure of the end portions of the channels, dependingon the structure of the filter module and the application.

It is especially noted that the filter module according to the presentinvention may be provided without any sort of supporting structure andthe inner peripheral surface of the filter module may constitute thepassage itself.

According to a further aspect of the present invention, however, it maybe advantageous to have a hollow support member supporting the innerperipheral surface of the body for specific filtration applications. Insuch cases the hollow support member preferably defines the passage ofthe body.

Such hollow support member may be made, for example, from organicsynthetic polymer material, which is inert with respect to the fluid tobe filtered. Examples for such polymeric material, which is preferablyused to produce the hollow support member, are polyethylene,polypropylene, polyamide, partly or wholly fluorinated hydrocarbonresins etc.

In a preferred embodiment, the hollow support member is a hollow shaft,the wall of the shaft being perforated in order to provide access forthe open ends of the channels opening to the inner peripheral surface ofthe body to the passage. At the same time it may serve as a means toclose the ends of the first type of channels which remain open at theouter peripheral surface of the body.

It has been mentioned before already for various times that the sheetmaterial may be compressible or non-compressible.

In a preferred embodiment, the sheet material comprises a matrixincluding a compressible material and/or a material which swells incontact with the fluid to be filtered.

In either case, compression of the sheet material during manufacturingand maintaining the sheet material forming the body in a compressedstate during operation of the filter module and/or the use of a materialwhich swells in contact with a fluid to be filtered, a body is providedwhich may be used as a depth filter unit avoiding the problem of bypass.

However, sheet material which is at least somewhat compressible ispreferred since such material may be formed to a body which may betested for bypass problems without having need to actually pass fluidthrough the filter module.

In contrast, the use of material which is swellable but essentiallyincompressible in the dry state requires bringing the material incontact with the fluid in order to provide the full function orcharacteristics of the filter unit.

According to still another aspect of the present invention the sheetmaterial may comprise a matrix incorporating an additive, said additivebeing preferably in particulate form.

Particulate form according to the present invention means any sort ofparticulate material being it, e.g., granular, fibrous or needle form.

The additive present in the sheet material amounts preferably up toabout 70% by weight, based on the weight of the sheet material.

The additives may be of organic or inorganic origin.

This very broad range of additives available allows for an easyadaptation of the sheet material to various filtration tasks and also toinfluence the characteristic of the sheet material with respect to itscompressibility or swellability.

Furthermore, the filter module may be used for functions different fromfiltration, especially for fluid treatment, including ion exchange,catalytic reactions and the like with or without taking advantage of thepossible filtration function of the module.

In a preferred embodiment of the present invention, the particulateadditive is selected from porous particulate additives, so as to providethe opportunity to perform specific filtration tasks.

In another preferred embodiment, the additive may comprise a filter aid,which allows for specifically designing the sheet material for selectedfiltration applications.

In another preferred embodiment of the present invention, the additivemay comprise a treatment agent which allows performing simultaneously toor instead of the filtration, a treatment of the fluid to be filtered.

In yet another embodiment, the additive comprises a reactive agent andthe filtration module then provides for the opportunity to convert acomponent included in the fluid upon or instead of filtration of thesame.

In another preferred embodiment, the additive may comprise an absorptiveor adsorptive agent, which allows for further adaptation of the sheetmaterial and its characteristic to a specific filtration task.

Examples for additives which may be used are kieselguhr, perlite,bentonite, activated carbon, zeolite, micro crystalline cellulose andPVPP (cross-linked polyvinylpyrrolidon).

Examples of filtration tasks for the various additives are as follows

PVPP is preferably used in the stabilization of beer, since it allowsremoval of polyphenols.

Activated carbon is used to, e.g., remove proteins, colorants, pyrogensetc. from the fluid to be treated.

Kieselguhr and micro-crystalline cellulose improve the removal rate forfine particles. Micro-crystalline cellulose is preferred in applicationswhere release of minerals from the additive into the filtrate might beof concern.

Perlite may be used to generate the so-called trubraum and improvesthereby the dirt holding capacity.

Zeolite is an appropriate and versatile additive for binding metal ions,water and the like, depending on the specific structure and compositionthereof.

Bentonite is a useful additive for the fining of wine.

Preferably the sheet material comprises a matrix including organicpolymer material. The organic polymer material may be a naturallyoccurring organic polymer material like cellulosic fibers. Syntheticpolymers, especially in the form of sintered or foamed polymericmaterials or organic fiber materials are also preferred organic polymermaterials.

Since many filtration applications need a sterile environment, in apreferred embodiment the sheet material is selected from sterilizablematerial, i.e. material which allows sterilization of the filtrationmodule without affecting the filtering characteristics of the module.

It has been explained before that the filtration module may be producedof the sheet material without having a support member for the numerouslayers of sheet material.

According to a further aspect of the present invention, however, it maybe advantageous to have a hollow support member supporting the innerperipheral surface of the body for specific filtration applications. Insuch cases the hollow support member preferably defines the passage ofthe body.

Such hollow support member may be made, for example, from organicsynthetic polymer material, which is inert with respect to the fluid tobe filtered. Examples for such polymeric material, which is preferablyused to produce the hollow support member, are polyethylene,polypropylene, polyamide, partly or wholly fluorinated hydrocarbonresins etc.

In a preferred embodiment, the hollow support member is a hollow shaft,the wall of the shaft being perforated in order to provide access forthe open ends of the channels opening to the inner peripheral surface ofthe body to the passage.

For quite a number of applications in the field of biopharmaceuticalsand others, e.g., prefiltration and fine filtration in enzyme productionprocesses, there arises the need to enhance and/or adapt the filterperformance to specific needs which often may be served by adding afilter aid, usually in the form of a powder or slurry, to the inletflow. The filter aid changes the character of the resulting mass ofsolids collected on the surface and within the structure of the filtermaterial in a manner which enhances the filtration characteristics ofthe filter. When this enhancement is accomplished by adding the filteraid to the process fluid to be treated, it is called a body feedprocess. When the enhancement is accomplished by adding the filter aidto a fluid that is conducted through the filter before the process fluidis introduced, it is called a precoat process. A precoat process may beconducted prior to filtering a process fluid using a body feed processand the fluid used for a precoat process may be different from or thesame as the process fluid.

Therefore, according to another aspect of the present invention, thefilter module comprises at least one type of channels, where the channelsurface supports a precoat, preferably in the form of a porous,essentially continuous layer. Most often such type of channels will bethe inlet channels.

If there is a continuous flow path created by areas of reduced thicknessor more specifically by compressed areas at the edge of the openings,such flow paths preferably also have a surface supporting a precoat.

If a macro-porous strip-like element is used to provide for the areas ofsmaller thickness, the surface provided by the macro-porous strip-likeelement also preferably supports a precoat which may be in the form ofan essentially continuous porous layer of said precoat material.

In a further preferred embodiment, the precoat comprises two or morecomponents. This provides for further possibilities to adapt theproperties of said material to specific tasks.

Preferably at least one of the components of the material is inparticulate form.

For specific applications, the precoat comprises a porous particulatecomponent. The porous particulate component may serve specific purposesto treat the fluid to be filtered and/or capture specific components ofthe non-filtrate.

Likewise the precoat may comprise a filter aid as a component inspecific applications.

In another embodiment, the precoat may comprise a treatment agent and/ora reactive agent as a component.

In still another embodiment, the precoat may comprise an absorptive oradsorptive agent as a component.

Examples for the afore-mentioned components for the precoat are thefollowing:

Kieselguhr, perlite, bentonite, activated carbon, zeolite,micro-crystalline cellulose and PVPP.

The aspects to select a specific component for the porous layer can beessentially the same as previously discussed in connection with theselection of additives for the sheet material.

The above described filter modules offer a versatile means toaccommodate a large number of specific needs, especially in the area ofbiopharmaceutical filtration processes or the fine filtration in enzymeproduction processes.

The deposition of a precoat, especially as a continuous layer of porousmaterial, on the surface of at least one type of the channels of thebody provides an inexpensive means to further enhance the filtrationperformance.

According to a further aspect of the present invention the filter modulepreferably comprises two end pieces to be sealingly positioned with afront face against the opposite ends of the passage in said body inorder to accommodate the body of the filter module in filter housings orother pre-existing environments. At least one of the end piecescomprises an opening to provide access to said passage.

The front faces of the end pieces may contain sealing elements in orderto sealingly engage the opposite ends of the passage of said body. Ifthe filter module is provided with a hollow support member, the endpieces may cooperate with the end faces of said support member.

Furthermore preferred is to have end pieces which comprise sealingflanges protruding from said front faces, said flanges being designed tocontact and optionally also compress at least the innermost layer of thesheet material thereby providing a sealing element free seal between thebody and the end pieces.

Said end pieces preferably additionally comprise a support flangeprotruding from the front faces and mating with the inner peripheralsurface of the body or the hollow support member. This embodiment isespecially designed to cooperate with the body of the filter module whena compressible sheet material is used. In such a case, the flanges mayhave a wedge-shaped cross section and penetrate at least partly theedges of the sheet material so as to compress the same providing for amore dense structure of the sheet material which enhances the sealingeffect.

In further preferred embodiments, the protruding flanges designed tocontact and compress two or more of the innermost layers of sheetmaterial of said body and the protruding flange may have a doublewedge-shaped structure of two concentrical wedge-shaped rings contactingtwo or more innermost layers of sheet material of said body.

In case a support member is used to support the inner peripheral surfaceof the body, it is preferred that the hollow support member has radiallyextending annular protrusions in its portions adjacent to the ends ofthe body so as to provide a form fit with the compressible sheetmaterial, avoiding slippage of the sheet material when the end piecesare sealingly engaging the ends of the body.

As explained earlier on, it is advantageous when the module iscompressed such that the body of wound layers constitutes a depth filterunit, once the sheet material is made of a depth filter material.

According to yet another aspect of the present invention clamping meansare positioned on the outer peripheral surface of the body in order tomaintain the compressed state of the sheet material of the filter body.

The clamping means may directly act on the outer peripheral surface ofthe body and preferably acts on those areas of the body comprising thesecond type of channels. This measure provides for additional safetyagainst bypass risks.

In another preferred embodiment, the clamping means directly act on theouter peripheral surface of all areas of the body except thosecomprising the first type of channels. This provides a maximum of safetyagainst bypass problems as outlined before. If the clamping means aremade of a fluid impervious material, it may be used to close the ends ofthe second type of channels at the outer peripheral surface of the body.In an alternative embodiment, closure of the second type channels may beprovided by a separate closure element on top of which the clampingmeans may be positioned.

In another embodiment, the areas of the body comprising outlet channelsare compressed to a greater extent than those areas comprising inletchannels. This provides for maximum flexibility to enhance the surfacearea on the inlet side of the filter module and provides maximum safetyagainst bypass problems likewise.

In a further preferred embodiment the clamping means comprise a sheetlike material including apertures to match the openings of the outermostlayer of sheet material, contributing to form inlet channels.

Furthermore preferable clamping means show a shrinkage characteristicsuch as to at least match the shrinkage characteristic of the body ofsheet material under sterilization conditions. Such a feature ensuresthat the compression of the body of sheet material is maintained even ifthe filter module has to undergo a sterilization process.

An example for a clamping means is a mesh type material or a perforatedfilm material.

Organic synthetic film material, e.g. shrink film, may be easily used asa clamping means.

Alternatively, strip-like material may be used to maintain the body ofsheet material in a compressed state.

In such case, preferably the openings of the different types of channelsare arranged in different rows in the sheet material so as to providedisk like areas of the body, where outlet channels are arranged, suchareas not comprising openings forming inlet channels.

In such an embodiment the strips are preferably positioned on the outerperiphery of the disk like areas of the body comprising the outletchannels.

In order to make maximum use in such a configuration of the sheetmaterial forming the body of the filter module, it is preferable thatthe body comprises in the vicinity of and spaced apart from its both endfaces a plurality of outlet channels. This provides for further filtercapacity in that the end faces of the filter module may be left open andin communication with the inlet side of the filer module, such facesalso contributing to the filtration capacity of the filter module.

It has been found out that strip-like or sheet like material made of apolymeric material may often have favorable properties with respect toshrinkage when it is used together with cellulosic type sheet materialforming the body, since the shrinkage effects observed with both type ofmaterial upon sterilization are similar.

While the individual layers of the body may be formed by individualportions of sheet material it is preferred that several if not all ofthe layers are formed of a continuous strip of sheet material spirallywound to form the body of the filter module.

According to a further aspect of the present invention the sheetmaterial constituting the body of the filter module preferably consistsof a unitary tape, i.e. one piece of tape only, having a first and asecond end portion, the first end portion being positioned and formingthe inner peripheral surface and the second end portion forming theouter peripheral surface of the body of the filter module. Preferably atleast one of those first and second end portions of the tape has asmaller thickness than those portions of the tape between those two endportions.

If the first end portion forming the inner peripheral surface, or atleast part of it, has a smaller thickness than those portions of thetape between the two end portions, a smooth winding is ensured startingfrom the innermost portion of the body of the filter module.

If the second end portion has a smaller thickness than those portions ofthe tape between those two end portions, especially the clamping meansare tightly abutting the outer peripheral surface of the body also inthe area, where the second end portion of the tape of sheet materialends.

Preferably, there is no stepwise configuration present at the second endportion of the sheet material.

In order to provide a very smooth transition, the first and/or secondend portions of the tape have a tapering cross section in the lengthwisedirection of the tape. Thereby a very smooth transition of the firstand/or last winding may be obtained.

The present invention furthermore relates to a process for themanufacture of the filter module as outlined above and such processcomprises:

forming the opening in the sheet material, reducing the thickness of thesheet material to a predetermined value in areas where openings areprovided for forming inlet channels and winding the sheet materialaround a support element to form a body of a multiplicity of consecutivelayers with an inner peripheral surface and an outer peripheral surface.

Reducing the thickness of the sheet material can be achieved indifferent ways.

In some cases it is preferable to carry out the thickness reducing priorto forming the openings. Depending on the nature of the sheet materialforming of the openings may be facilitated.

With some sheet materials the thickness reducing can be carried outafter forming the openings.

In many cases the thickness reducing can be carried out simultaneouslywith the formation of the openings. Especially preferred is the use of apunching tool to form the openings, the punching tool being providedwith compression elements for compressing the sheet material in theareas of openings for forming the inlet channels.

As a further alternative the thickness reducing can be carried out whilewinding the sheet material to form said body.

As an alternative to deformation or compression of the sheet materialprior to winding the same to form the body of the filter module, a firststrip-like element of a macro-porous material may be co-wound with thesheet material to cover the areas of the sheet material comprising theopenings forming inlet channels. By co-winding the macro-porous materialin strip-like form, automatically a compression of the sheet material inthe area comprising the openings forming inlet channels is achieved anddue to the macro-porous character of the material, the surface area ofthe sheet material is still accessible to the fluid to be filteredwithout hindering the fluid essentially to contact the sheet materialsurface on the inlet side of the filter module. Optionally, thestrip-like element may comprise openings essentially matching theopenings of the sheet material.

The term macro-porous as used in this context means anythree-dimensional open-pored structure which does not contributenoticeably to the filtering effect and which preferably essentiallypresents no flow restriction to the fluid in the inlet channels.

Preferably said macro-porous element comprises openings essentiallyregistering with the openings forming the inlet channels. In this casethe macro-porous element adds as little as possible to pressure drop anddoes not disturb fluid flow to the inlet channels.

Most preferably the thickness reducing comprises reducing the thicknessof the sheet material from both sides of the sheet material. Therebyformation of ring shaped channel structures interconnecting a pluralityof inlet channels is greatly supported.

In order to provide further security with respect to the bypass problem,a second strip-like element may be co-wound with a sheet material tocover the areas of the sheet material comprising the openings formingthe outlet channels. The second strip-like element may be used togetherwith the first strip-like element or independent of the same. The secondstrip-like element provides for a compression of the sheet material inthe area of the outlet channels serving for an intimate contact of thesheet material around the openings forming the outlet channels whichprovides for additional safety against unwanted bypasses.

The material from which the second strip-like element is made, may bethe same as the sheet material, since the material from which the secondstrip-like element is made need not necessarily be incompressible as themain function of the second strip-like element is to provide additionalcompression forces in the areas of the outlet channels so as to providefurther security against bypasses.

The second strip-like element therefore may be made of a depth filtermaterial, but may also be in some applications made of an essentiallynon-porous material. In addition, the second strip-like element may bemade of a material which is essentially incompressible.

According to a preferred embodiment during winding the sheet materialaround a support element to form a body of a multiplicity of consecutivelayers with an inner peripheral surface and an outer peripheral surface,the sheet material is compressed by a compression force when woundaround the winding axis to provide intimate contact of each of thelayers to the adjacent layer(s), said compression force being applied ina radial direction by a roller.

It is important according to the process of the present invention toapply the compression force in a radial direction by way of a roller,co-rotating with the body of sheet material during the winding process.Then not only a carefully controlled compression force may be applied,but also the sheet material is treated very carefully, and sheetmaterial may be used which does not need to have high tensile strength,since the compression force is separately applied and need not becreated by tensile forces exerted on the sheet material.

It has been found that a compression of the sheet material, such thatthe thickness of the compiled layers of the body amounts to about 99% orless of the thickness of the same number of individual layers of sheetmaterial is often already enough to solve the bypass problem. Asexplained in detail above, the amount of compression needed is of coursedepending on the compressibility of the sheet material itself so thatwith easily compressible sheet material a more pronounced compression ofthe body may be advantageous.

However, usually the thickness of the compiled layers of the compressedbody will amount to about 20% or more of the thickness of the samenumber of individual layers of sheet material. If the compression ishigher than that limit, there might result an undesirable high reductionin the dirt retention capacity. On the other hand, a high compressionimproves the filtration efficiency for smaller particles. Therefore, themodification of the compression force exerted by the roller is a meansto adapt the filtration characteristics of a given sheet material tospecific filtration applications.

A further preferred limit to compress the body corresponds to about 50%or more of the thickness of the compiled individual layers of sheetmaterial. A compression within this limit is easier to be handled withrespect to the filter characteristics to be achieved.

Nevertheless, often enough with compressible sheet material compressionto a thickness of about 85% or more of the compiled individual layerswill provide very good results. In a large number of cases, thecompression preferably amounts to a thickness of the compiled individuallayers of about 97 to about 85%.

The above described and further advantages of the present invention willbe apparent from the following description of the figures of thedrawing. The individual figures show:

FIG. 1: A first embodiment of an inventive filter module with a body ofwound layers of sheet material;

FIG. 2: a schematic representation of several layers of sheet materialof the filter module of FIG. 1;

FIGS. 3 a, 3 b and 3 c: a partial cross-section through several layersof the sheet material of the filter module of FIG. 1;

FIG. 4: an alternative embodiment to the structures shown in FIGS. 3 ato 3 c;

FIG. 5: a partial cross-section through a filter module according toFIG. 1;

FIG. 5 a: a modification of the filter module of FIG. 5;

FIG. 6: partial schematic cross-sectional representation of variouslayers of sheet material of a filter module according to a furtherembodiment of the present invention;

FIG. 7: partial cross-section of an end portion of a filter moduleaccording to FIG. 1; and

FIG. 8: a schematic representation of part of the manufacturing processof the filter modules according to the present invention.

FIG. 1 shows a filter module 10 of the present invention, comprising abody 12 of wound layers of a sheet material 13.

The body 12 of filter module 10 comprises an inner peripheral surface 14and an outer peripheral surface 16. Within the body 12 there is apassage 18 which extends through the body 12 along its winding axis 20,coextensive with the inner peripheral surface of the body. The innerperipheral surface of the body is in fluid communication with thepassage 18 which is constituted in the embodiment of FIG. 1 by a supportmember in the form of a hollow, perforated shaft (not shown in FIG. 1).

The sheet material 13 comprises a large number of openings 22 which incase of the embodiment shown in FIG. 1 are of circular shape,cooperating to form a first type of channel 24 which opens to the outerperipheral surface 16. Channels 24 generally extend in the directionfrom the outer to the inner peripheral surface of the body 12.

The sheet material 13 furthermore comprises a plurality of openings 26,cooperating to form a second type of channels 28 which open to the innerperipheral surface 14 of the body 12 (cf. FIG. 5). Channels 28 generallyextend in the direction from the inner to the outer peripheral surfaceof body 12.

For ease of reference, the first type of channels 24 will be calledinlet channels, the second type of channels 28 will be called outletchannels.

It has, however, to be noted that it is within the scope of the presentinvention that the channels 24 which open to the outer peripheralsurface 16 may function as outlet channels, whereas the channels 28which open to the inner peripheral surface 14 than serve as inletchannels. The fluid flow would then be reversed from passage 18 intochannels 28, through the body 12 of sheet material 13 and the outletchannels 24 collecting the filtrate and draining it to the outerperipheral surface 16.

Preferably, the openings 22 and 26 are arranged in the sheet material 13in parallel rows so that the inlet and outlet channels 24 and 28,respectively, are formed in separate disk shaped portions 29 a and 29 bof the body 12.

On both of its front faces 48 the filter module 10 is supported by endpieces 150 which will be described in further detail in connection withFIG. 7.

FIG. 2 schematically shows three layers of sheet material 13 of thefilter module 10 of FIG. 1. While in the representation of FIG. 1 forsimplicity reasons only a single row of openings forming inlet channelsare shown, FIG. 2 shows in more detail a preferred opening pattern forthe inlet channels 24.

Layer 30 a corresponds to an outermost layer of sheet material 13constituting the outer peripheral surface 16.

Layer 30 d is an intermediate layer of the body 12 and layer 30 zcorresponds to an innermost layer constituting the inner peripheralsurface 14 of the body 12.

Of course, the body 12 of filter module 10 usually has a much largernumber of layers 30 but the afore-mentioned layers 30 a, 30 d and 30 zshow all details necessary to explain the function of the inventivefilter module 10.

In order to make full use of the sheet material 13 in the filter module,groups of three parallel rows of openings 22 a, 22 b and 22 c areprovided, the openings being of circular cross section.

In order to further maximize use of the sheet material 13, these threerows of openings 22 a, 22 b and 22 c could be arranged within theirgroup of rows in a staggered configuration which is shown and furtherdiscussed in connection with the representation of FIG. 3 b.

FIG. 2 mainly serves the purpose to explain the fluid flow through thebody of sheet material 13 of filter module 10 rather than to givespecific other details of the construction of the filter module.

As noted before, the outer layer of sheet material 30 a constitutes theouter peripheral surface 16, is exposed to inflowing fluid to be treatedand only comprises openings 22 contributing to the formation of inletchannels 24. The innermost layer 30 z, constituting the inner peripheralsurface 14, comprises only one type of openings, namely openings 26,participating in forming outlet channels 28.

The fluid flow through the body 12 of filter module 10 is schematicallyshown by arrows 80, 82, 83 and 84. Inflowing fluid is divided up intothe various streams entering the inlet channels 24.

The fluid to be treated after entering the inlet channels 24 over thewhole surface 16 flows into the body 12 of filter module 10. Since theinlet channels 24 are closed off by the innermost layer 30 z of sheetmaterial 13, the fluid flow cannot continue through the inlet channels24 into the passage 18 which is in fluid connection with the interiorperipheral surface 14.

Therefore, the fluid flow distributes and continues migrating throughthe sheet material 13 as indicated by arrows 82 until it reaches anoutlet channel 28 constituted by openings 26.

In the outlet channels 26, the filtrate is collected and drained to theinner peripheral surface 14 where it is combined as indicated by arrow84.

Since it is of importance to have a large surface area available on theinlet channel side, the number of inlet channels 24 in this embodimentis approximately threefold of the number of outlet channels 28, the sizeof the openings 22 and 26 being approximately the same.

Also shown schematically in this drawing is that at the end faces 48 ofthe body 12 there is preferably a row of outlet channels 28 arranged soas to make use of the end faces 48 of the body 12 and have themparticipate in the filtration process.

This is indicated by arrows 83, representing flow from the end faces 48of the body 12 to the outlet channels 28.

FIGS. 3 a to 3 c and 4 represent two layers of sheet material 13 of afilter module 10 cut out from the middle of body 12 of the filter modulein FIG. 1 to explain the main aspect of the present invention.

Inflowing fluid enters the body 12 of sheet material 13 via the inletchannels 24, which are arranged in parallel rows. In some embodiments,the three rows of inlet channels 24 are arranged in a staggeredconfiguration so as to use minimum portions of the area of the sheetmaterial 13 for providing a maximum of surface area on the inner channelside without affecting the mechanical stability of the body 12.

The outlet channels 26 are arranged as single rows of parallel channelssince increase of surface area is mainly of concern for the inlet side.

FIGS. 3 a to 3 c show various modifications of the inlet and outletchannel structures proposed by the present invention. The area at theedges of the openings forming the inlet channels and in FIG. 3 b alsofor the outlet channels has been reduced to a predetermined thickness.

In FIG. 3 a, the sheet material 13 comprises a single row of inletchannel openings 22 alternating with single rows of openings 26 formingoutlet channels 28. In order to provide sufficient surface on the inletside of the filter module 10, the cross-section of the openings 22 ismuch larger than the cross-section of the openings 26 forming the outletchannels 28.

Furthermore, the thickness of the sheet material 13 at the edges of theopenings 22 forming inlet channels 24 has been reduced on both sidesthereof to a predetermined thickness. The areas around the openings 22with reduced thickness form a continuous channel-like structure 90.

Because of this, the surface area available is greatly increased sincethe surface area 90 around the openings 22 forming inlet channels 24also contributes to the surface area where the inflowing fluid maydirectly and unabstractedly contact the surface of the sheet material13. Two adjacent layers of the sheet material 13 then provide acontinuous spiral channel 92 interconnecting the inlet channels 24formed by one row of openings 22.

The fluid flow within the sheet material 13 not only occurs between thewalls of the openings 22 in direction to the outlet channels 28 but alsofrom the areas around the edges of the openings 22, having a reducedthickness.

As may be seen from FIG. 3 a quite clearly, the reduced thickness of thesheet material when provided on both sides of the sheet material 13increases the surface area available for inflowing fluid for penetratinginto the sheet material 13.

As described before already, the filtrate is collected in the outletchannels 28 and drained to the inner peripheral surface 14 and passage18 which both are not shown in FIG. 3 a.

In FIG. 3 b, an opening pattern comprising three parallel rows ofstaggered inlet openings 22 has been provided in the sheet material 13,where, however, areas 94 and 95 of reduced thickness of the sheetmaterial are present not only in the areas around the edges of theopenings 22 forming inlet channels 24, but also around the edges of theopenings 26 forming outlet channels 28.

In this specific embodiment, the reduction of the thickness of the sheetmaterial 13 has been provided only on one side of the sheet material 13.

The cross-sections of the openings 22 forming the inlet channels 24 andthe openings 26 forming the outlet channels 28 are approximately thesame. However, because of the increased number of inlet channels 24 withrespect to the available outlet channels 28, the surface area availableon the inlet side is much larger than on the outlet side.

FIG. 3 c shows another modification of the area 96 of reduced thicknessaround the inlet openings 22 whereas the thickness in areas around theopenings 26 forming the outlet channels 28 has not been reduced. Thereduced thickness has been provided on both sides of sheet material 13.

It may be seen from this embodiment that a broad variety ofconfigurations of areas of reduced thickness around the edges of theopenings in the sheet material 13 forming inlet channels 24 is availableand may be selected according to the filtration task to be performed.

FIG. 4 shows another embodiment of the present invention in the form ofa filter module 110 which is shown only with a part of its body 112represented by two adjacent layers of sheet material 113 were taken outof it similar to FIGS. 3 a to 3 c.

Therefore, both layers of sheet material 113 have opening patternsincluding openings 118 constituting inlet channels 120 as well asopenings 114 forming outlet channels 116.

In order to provide an increased surface area on the inlet side,strip-like elements 122 of macro-porous structure have been co-woundwith the sheet material 113 in order to provide for compression of thesheet material 113 in the areas around the openings 118 forming theinlet channels 120.

Because of the reduced thickness of the sheet material 113 around theinlet channels 120, the filter area has been increased. In order tofurther maximize the surface area on the inlet side, the diameter of theopenings 118 can be made larger, while the diameter of the openings 114forming the outlet channels could be made smaller.

In order to allow a smooth winding of the strip-like material togetherwith the sheet material 113 and in order to allow an essentially smoothouter surface of the body 112 the strip-like elements 122 have a doublewedge-shaped cross-section, the tapered edges of which pointing in thedirection of the outlet channels 116.

The strip-like elements 122 may be divided in two parallel portions asis shown in FIG. 4 but they may also be of a unitary structure and havea double wedge-shape as is easily feasible from the representation ofFIG. 4.

In the case of the divided structure of the strip-like elements 122 asshown in FIG. 4, there is provided a spiral channel 124 between theadjacent layers 113 interconnecting the inlet channels 120 of each rowof openings 118 so that the filtrate enter the sheet material 113 in thearea of the inlet channels 120 may also circulate in between theseareas.

From FIG. 5 it is apparent that the openings 22 forming inlet channels24, incompletely register with corresponding openings 22 of an adjacentlayer of sheet material 13. For simplicity reasons the reduced thicknessof sheet material 15 in the areas of the edges of openings 22 is notshown.

The inlet channels 24 are closed on their ends 34, located adjacent tothe inner peripheral surface 14 of body 12 and not in communication withsaid passage 18. Correspondingly, the outlet channels 28 are open attheir ends adjacent to the inner peripheral surface 14, but are closedat their opposite ends 36 adjacent to outer peripheral surface 16. Inorder to provide this structure of channels 24 and 28 in the body 12 ofthe filter module 10, the sheet material 13 comprises in a first endportion 38 openings 26 only which contribute to forming the outletchannels 28. No openings which could contribute to forming inletchannels 24 are found in that portion 38 of sheet material 13.

At its other end portion 40, the sheet material 13 comprises openings 22only contributing to form inlet channels 24, and in that end portion 40no openings 26 which contribute to forming outlet channels 28 are found.

Usually, the length of the end portions 40 and 38 is such that theclosed ends 36 and 34 of the outlet and inlet channels, respectively,are covered and shut off by at least two consecutive layers of sheetmaterial 13 within the body 12 adjacent to the inner peripheral surface14 and the outer peripheral surface 16, respectively.

This is usually enough to ensure that the filter characteristic of thebody 12 as a whole is maintained and no fluid to be treated may bypassthe sheet material and find a shortcut from the inlet of the filtermodule 10 to the outlet of the filter module.

The filtering operation of the inventive filter module 10 has beendescribed in some more detail in connection with FIG. 2 already.

As can be seen from FIG. 5, the openings 22 of adjacent layers 30 a, 30b, 30 c and 30 d incompletely register such that the surface of inletchannel 24 does not show a smooth tubular surface but comprises theplurality of recesses 41 a and projections 41 b, respectively,increasing the surface area of the inlet channels 24 to a great extent,thereby increasing the filter capacity and the service life of thefilter module 10.

Other methods of ensuring incomplete registration of the openings arepossible and are included in the constructions envisioned in thispatent. For example multiple punches, each having a somewhat differentsize cross-section and/or cross-sectional shape could be used to createopenings which vary in size and/or shape from one opening to the next.When wound to form the body, the edges of these openings do notcompletely register, due to their differing sizes, any off-set in theirlocations and/or differing shape.

Likewise apparent from FIG. 5 is the gradually reduced thickness of theend portion 38 of the sheet material 13 at its very end, which maylikewise be true for the end portion 40 at the outer peripheral surface16 of body 12.

By having the end portions 38 and 40 with tapered sections 42 and 44,respectively, a smooth winding of the sheet material 13 is providedwhich contributes to a full contact of adjacent layers of sheet material13 throughout the body 12.

The tapered portion 44 of end portion 40 of the sheet material 13 at theouter peripheral surface 16 of body 12 provides for a smooth outersurface 16, not comprising any step-like recesses on that surface.

This is of importance, once the body 12 of the filter module 10 is holdin compression by strip-like elements 46 which serve to keep the sheetmaterial 13 of body 12, and therefore the body 12 as a whole, in acompressed state such that bypasses from inlet channels 24 to outletchannels 28 are avoided.

The strip-like elements 46 function as compression means and arepositioned on the outer peripheral surface 16 of body 12 on such diskshaped portions 29 a of the body 12 which comprise the outlet channels28. The portion 29 b of the body 12 comprising the inlet channels 24 arenot covered by this strip-like elements 46. Therefore the compression ofthe body 12 in the areas 29 a comprising the outlet channels 28 issomewhat higher than in the portions 29 b of body 12 accommodating theinlet channels 24. This is of some importance for avoiding bypassproblems, and the fluid to be filtered is forced to migrate through thesheet material 13 prior to reach the outlet channels 28 and the passage18.

The tapered end portion 44 of the end portion 40 of the sheet material13 helps to apply the compression force of the strip-like elements 46around the whole outer peripheral surface 16 in an even fashion whichmakes sure that the body 12 has homogenous filter characteristicsthroughout the whole body.

The sheet material 13 of body 12 may be a depth filter material or maybe a non-porous material depending on whether the filter module is towork as a depth filter unit or a surface filter unit.

Most of the depth filter materials useful in the present invention maybe compressed or deformed. The portion of deformation, which ispermanent, differs depending on the depth filter material used.

Preferably, the depth filter material is not only plastically orpermanent deformable, but at least partly shows elastic properties sothat upon compression of the sheet material 13, the elastic portion ofthe deformation helps to keep the adjacent layers of sheet material 13in close contact with one another, although the surface of the sheetmaterial 13 may in its original state not be perfectly planar.

The preferable depth filter material used according to the presentinvention may have different basic structures. For example, nonwovenfiber material may be used on the basis of melt blown fibers, cellulosicfibers or other naturally occurring fibers, organic or inorganic fibers,metal fibers, glass fibers, ceramic fibers, etc.

Also woven materials are possible with various fiber structures. Thewoven material may be monofil material, multifil material and/ormultilayer material The basic materials may be cellulosic material, orother naturally occurring fibers, organic or inorganic fibers, thelatter including metal fibers.

Also sintered materials may be a suitable depth filter material for useas sheet material 13 including sintered woven materials, sintered powdermaterials of different structure and particle sizes, mainly made ofplastic or metal.

Furthermore, foamed material of plastic or naturally occurring polymersof different structure may constitute a sheet material useful in thepresent invention.

Depth filter materials manufactured of the basis of cellulosic fibersmay be compressed substantially, i.e., very well below about 200% oftheir original thickness without destroying integrity of the filterlayers. The degree of maximal compression of course depends on thepresence or absence of additives combined with the cellulosic fibers.Such additives may very well be incompressible and may occur in amountsof up to about 70% by weight, based on the weight of the sheet material.

Cellulose based sheet materials are well suited for the presentinvention. They may be compressed to a thickness of, e.g., about 12% ofthe original thickness, using a compression force of 2700 N. When thosematerials are allowed to recover a thickness of about 20% of theoriginal thickness, the elastic force amounts, e.g., to 530 N.

Other examples of useful cellulose based sheet materials, which may beused according to the present invention as sheet material 13 to form thebody 12 may be compressed to a thickness of about 33% with a compressionforce of 3600 N and show a elastic force when released to a thickness ofabout 45% of its original thickness of 250 N.

Cellulosic material usually swells when contacted with aqueous media andin the latter example, the elastic force may be increased by theswelling effect to 310N.

In an application where the sheet material 13 will not swell in contactwith the fluid to be filtered, a somewhat higher compression willusually be used than in cases where the sheet material swells when incontact with the fluid to be filtered. This is often sufficient toensure a safe operation of the filter module 10.

FIG. 5 a shows a filter module 10″ having a structure similar to thefilter module shown in FIG. 5. Therefore, the description given abovewith reference to FIG. 5 also applies with the following exceptions:

In contrast to the embodiment shown in FIG. 5, the filter module 10″comprises inlet channels 24′ which extend down to the inner peripheralsurface 14 where they are closed by a fluid impervious portion ofclosure element 35, which optionally may function as a support memberand have the form of a hollow, perforated shaft. Perforations 27 of thesheet or closure member 35 register with openings 26 of the sheetmaterial being part of the outlet channels 28. The sheet material usedfor forming filter module 10″ does not have an end portion 38 whereopenings 22′ contributing to the inlet channels are missing as it is thecase in the embodiment of FIG. 5.

Likewise, in contrast to the embodiment of FIG. 5, the sheet materialused to form the filter module 10″ does not have and end portion 40where openings contributing to outlet channels 28 are missing.

The closure of the outlet channels 28 on the outer peripheral surface 16of body 12 is provided by a closure element which optionally mayfunction as compression means (strip like element 46).

Preferably, also in case of filter module 10″, end portions of the sheetmaterial have a tapered configuration as shown in FIG. 5 (referencenumerals 42 and 44).

It is well understood that the afore-described alternative closure ofthe inlet and outlet channels on the inner and outer peripheral surfaces14, 16 of the body 12 may also be put into practice with any otherchannel configuration within the scope of the present invention.

Another aspect of the present invention is shown in FIG. 6 in the formof a partial cut out of a body 132 of a filter module 130. The body 132comprises a spirally wound sheet material 134 which is provided withopenings 136 forming inlet channels 138 which are separated by stays 140in the longitudinal direction of the sheet material 134. In the exampleshown in FIG. 6, the openings 136 are relatively large and ofrectangular configuration. In view of the size of the openings,especially their extension in the direction of the longitudinal axis ofthe sheet material 134, it is conceivable that the stays 140 meet thecorresponding stay of the adjacent layer of sheet material 134 is of noconcern for the present invention. For simplicity reasons the sheetmaterial around the openings 136 forming the inlet channels 138 is shownwith a unitary thickness only. However, it is easily conceivable thatthe enlarged surface area provided by reduced thickness of she sheetmaterial in areas at the edges of the openings 136 will give rise to anenlarged surface to be coated with the porous layer 146.

The stays 140 mainly serve to stabilize the structure of the body 132and they serve this purpose irrespective of whether they meet with staysof adjacent layers of sheet material 134 or not.

Furthermore, the sheet material 134 comprises rows of openings 142forming outlet channels 144. The special aspect of the embodiment shownin FIG. 6 is that the surface of the inlet channels 138 are covered by aporous layer 146 on the surface portions of the inlet channels 138facing the outlet channels 144.

This porous layer may be deposited by a precoat process, a body feedprocess, or some combination of the two. It may also contain matterfiltered from the process fluid during a body feed process. Any suchlayer containing material specifically added by a precoat or body feedprocess is usually called a precoat layer or simply a precoat. Theprocess of creating a precoat is often called precoating.

One example of a body feed process is to start the process of filteringthe fluid product and then inject into the flow, through a mixing valveupstream of the filter, a continuous supply of filter aid powder mixedwith water (or other appropriate fluid). The volume flow rate of themixture of water and powder would typically be small compared to thevolume flow rate of the process fluid. A precoat process that is not abody feed can be accomplished similarly. For example, the supply offilter aid powder mixed with water can be fed through the filter systembefore the process fluid is introduced into the system. Once asufficiently thick precoat is achieved in the filter channels, the feedof filter aid mixed with water is stopped and the filtration of processfluid is begun.

The precoat of the inlet channels 138 may be constituted of variousmaterials depending on the specific treatment or filtration applicationand may include filter aid, reactive agents, treatment material,absorptive or adsorptive matter or other components.

Particularly preferred is a particulate material for the componentsconstituting the precoat layers 146 and specific examples for suchcomponents are kieselguhr, perlite, bentonite, activated carbon,zeolite, micro crystalline cellulose and PVPP.

Precoating of the inlet channels 138 provides for a versatile means toadapt the properties of the body 132 to various treatment and/orfiltration tasks.

Treatment of fluid may be performed by a filter module 130 takingadvantage of the filtration characteristic of the body 132 or not.

The combined filtration characteristics of the filter media and theprecoat depend on many factors including the nature of the process fluidand the flow, pressure and temperature specifications of the filtrationprocess. Of particular relevance to the present invention, thefiltration characteristics are affected by the thickness of the precoatand what the remaining size of the openings 136 are after accounting forthe precoat thickness. In many processes, optimal performance isobtained when the precoat remains thin compared to the size of theopenings 136. However, depending on the porosity and othercharacteristics of the precoat, an optimal process may be to completelyor nearly completely fill the openings 136.

Yet another aspect of the present invention is shown in FIG. 7.

As has been explained in connection with the description of theembodiment shown in FIG. 1 already, the passage 18 is extending throughthe filter body 12 from one end face 48 to the other.

In order to accommodate the body of the filter module 10 within ahousing, especially in a pre-existing housing or in a pre-existingfilter assembly, it is necessary to provide an adaptation of the passage18 to the (pre-existing) environment. An option for such adaptation isshown in FIG. 7. According to the proposal shown in FIG. 7, end pieces150 sealingly engage the end faces 48 of the body 12 in their centralportion. The end pieces, at least one of which comprising an opening toprovide an access to passage 18 also engage, as shown in FIG. 7, thesupport member 32, if present.

While the end pieces 150 may comprise a sealing element, it is preferredas shown in FIG. 7 to provide the end pieces with sealing flanges 152,154 projecting from their front faces directed to the end faces 48 ofthe body 12.

The flanges 152 and 154 preferably have the conical shape as shown inFIG. 7 in their cross-section which enables them to protrude into theedges of layers of sheet material 13 which consequently is compressedcreating a higher flow resistance to fluid to be treated or filtered.

The innermost protrusion 154 is preferably designed larger than theprotrusion 152.

The support member 32 shows a tapered portion 33 so as to provide somespace for the sheet material 13 forming the innermost layer 13 a toyield upon protrusion of flange 154 into its edge.

When a support member 32 is used to define the passage 18, as it is thecase in FIG. 7, such support member has on its end portions adjacent toend faces 48 of body 12 angular protrusions 160 which ensure that thesheet material 13 is hold in place with respect to the support member 32when the end pieces 150 are mounted on the end faces 48 of the body 12and the protruding flanges 152 and 154 enter the edge of the layers ofsheet material 13 while compressing same.

A still further aspect of the present invention is shown in FIG. 8.

FIG. 8 gives a schematic representation of the manufacturing process forthe filter modules described above.

The process according to the present invention is described in thefollowing for a cellulosic filter material to be used to form the bodyof the filter modules according to the present invention. Suchcellulosic sheet material 13 is provided from a storage roll 170 andtravels from that storage roll 170 to a punching machine 172, comprisinga punching tool 174 for forming the openings for the inlet and outletchannels of the filter module to be created.

Preferably, as mentioned before, the punching tool 174 comprisescompression elements (not shown) to allow deformation of the sheetmaterial 13 around the areas of opening forming inlet channels and/oroutlet channels as explained before in connection with, for example,FIGS. 3 a to 3 c. Downstream of the punching machine 172, the punchedsheet material 13′ is provided to a winding machine 176 which takes upthe punched sheet material 13′ and winds it to the final filter module.Alternatively the areas of reduced thickness at the edge of the openingsforming the inlet channels could be formed in a separate step eitherbefore or after the formation of the openings.

During the winding process, it is important to ensure close contactbetween the adjacent layers of sheet material 13′ and to apply acompression force in radial direction by a roller 178.

The compression force exerted by roller 178 is to be the radialdirection as indication in FIG. 8 by arrow 180.

Preferably, the roller 178 does not create friction and the area inwhich the compression force 180 is applied and sensed by the sheetmaterial 13′ upon winding and the forming of the filter module shouldextend over an area beyond the actual contact point or contact line ofroller 178 and the winding of filter module 10.

After the filter module 10 has been completed, the sheet material 13′will be cut along a line perpendicular to the travelling direction ofthe sheet material 13′, filter module 10 will be still maintained in thecompressed state, taken from the winding station 176 and compressionelements will be put in place in order to maintain the body of filtermodule 10 in a compressed state.

The punching tool 174 is operated such as to create in the beginning ofthe winding process only openings for channels which are to communicatewith passage 18 of filter module 10, but not such openings which are toform channels of the type which will be in communication with the outerperipheral surface of the body of the filter module 10.

This punching operation will be continued until a length of sheetmaterial 13 has been punched which will form approximately two layers ormore of the body of wound filter material of the innermost portion ofthe body of filter module 10.

Thereafter, the punching operation of the punching machine 172 will beswitched to full operation, i.e., punching not only the openings for thechannels open to the passage 18 and the inner peripheral surface offilter module 10, but also the openings for channels to open to theouter peripheral surface of filter module 10.

Near the end of the winding process, the punching operation is againchanged such that only openings forming channels, which are open to theouter peripheral surface 16 of the filter module, will be produced, butopenings forming channels which open to the passage 18 of filter module10 will no longer be produced anymore.

This operation is continued for such a time that approximately two ormore layers of sheet material 13′ are being wound on the body of filtermodule 10, which only comprise the openings forming channels which opento the outer peripheral surface of the body of filter module 10.

As noted before, the end portions of the sheet material 13′ may be intapered form such that the front portion of the sheet material 13′,which is wound to form the filter module 10 in the winding machine 176,will not create a step-like structure in the body of filter module 10,but will allow a smooth winding of the sheet material 13′ in spiralform. Also the very end portion of the sheet material 13′ which is woundon the body of filter module 10 will have a tapered section such thatthere is smooth surface achieved on the outer peripheral surface of thefilter module 10, avoiding a stepwise structure and ensuring that thecompression elements fixed on the outer peripheral surface 16 of module10 will closely abut against all of the surface portions they aresurrounding.

The compression force 180 imparted on the sheet material when wound inwinding machine 176, may be adjusted in order to obtain the desireddegree of compression of the body of the filter module 10.

The degree of compression is determined by the proposed application andthe nature of the sheet material 13 used in this winding process.

While in connection with FIG. 8 the process of the present invention isdescribed in connection with a step-wise punching operation of thepunching machine 172, it is easily conceivable that a continuouspunching operation may be performed. Of course, then the punching toolwould have to look differently, but again also in such type of punchingprocedure, it would be possible to switch on and off individual punchingtools for forming the openings for one type of channel and/or the other.

However, punching in the intermitting fashion as shown in FIG. 8 ispreferred since it easily allows to provide the openings in a mannersuch that the openings, when wound to form a body for the filter module10, incompletely register with one another, at least to the extent theopenings of the inlet channels are concerned. The advantages achieved bysuch method are explained in detail in the general description of thepresent invention.

This would require in the punching operation as described in connectionwith FIG. 8 that between two strokes of the punching tool 174, the sheetmaterial to be punched is adjusted in its position with respect to thepunching tool such that adjacent openings forming the same type ofchannel do have a different distance in the lengthwise direction of thesheet material 13 than two adjacent openings of the same type showwithin one punching patter produced in one punching operation of thepunching tool 174. The distance may be larger or smaller, but the effectwhen the punched sheet material 13′ is wound to form the body of thefilter module 10 will result in an incomplete registering of theopenings as is shown best in FIG. 5.

1. A filter module comprising a body of wound layers of a sheetmaterial, said body having an inner peripheral surface and an outerperipheral surface, a winding axis and a passage extending along thewinding axis of said body and in fluid communication with said innerperipheral surface, said sheet material having a plurality of openingsformed therein, said openings forming two types of channels within thewound layers of sheet material of said body, said channels extending ina direction from the inner peripheral surface to the outer peripheralsurface, a first type of channels being open at one end at said outerperipheral surface of the body and closed at the other end locatedadjacent to said inner peripheral surface, a second type of channelsbeing open at one end at said inner peripheral surface of the body, influid communication with said passage and closed at the other endlocated adjacent to said outer peripheral surface, said channels of theone type being separated from the channels of the other type by portionsof sheet material, one of said types of channels being inlet channelscommunicating with a fluid inlet of said filter module, the other ofsaid types of channels being outlet channels communicating with anoutlet of said filter module, the module having twofold or more inletchannels as compared to outlet channels, wherein the sheet material hasareas at an edge of the openings forming the inlet channels, thethickness of the areas being smaller than the thickness of the sheetmaterial remote from the openings foaming the inlet channels.
 2. Thefilter module of claim 1, wherein the areas of sheet material of smallerthickness at the edge of the openings forming the inlet channels arecompressed to a predefined thickness.
 3. The filter module of claim 1,wherein the areas of smaller thickness of the sheet material radiallyextend to openings forming the outlet channels.
 4. The filter module ofclaim 1, wherein the areas of smaller thickness extend to adjacentopenings of the same type, said areas forming one or more continuousflow paths extending along the winding direction of the sheet material.5. The filter module of claim 1, wherein a first strip-like element of amacro-porous material is co-wound with the sheet material to cover theopenings of the sheet material forming inlet channels.
 6. The filtermodule of claim 5, wherein the macro-porous material is essentiallyincompressible.
 7. The filter module of claim 5, wherein the firststrip-like element has the form of a band having a wedge-shapedcross-section.
 8. The filter module of claim 1, wherein both sides ofthe sheet material are compressed while winding the layers to form thewound layers.
 9. The filter module of claim 1, wherein a secondstrip-like element is co-wound with the sheet material to cover theopenings of the sheet material forming the outlet channels, saidstrip-like element having openings to essentially register with theopenings of the sheet material.
 10. The filter module of claim 9,wherein the second strip-like element is made of a non-porous material.11. The filter module of claim 9, wherein the second strip-like elementhas the form of a band having a wedge-shaped cross-section.
 12. Thefilter module of claim 1, wherein a majority of the openings forming theinlet channels incompletely register with corresponding openings of anadjacent layer of sheet material.
 13. The filter module of claim 12,wherein the incomplete registering of the openings corresponds in theaverage to an overlap of the openings of about 90% or less.
 14. Thefilter module of claim 12, wherein the incomplete registering of theopenings corresponds, in an average, to an overlap of about 50% or more.15. The filter module of any one of claim 12, wherein at least about 75%of the openings forming the inlet channels incompletely overlap with thecorresponding openings of an adjacent layer.
 16. The filter module ofclaim 1, wherein said openings are separated from one another by staysof sheet material.
 17. The filter module of claim 16, wherein theopenings forming the inlet channels have an extension in a windingdirection of the sheet material longer than an extension of the staysseparating these openings from one another in the same direction. 18.The filter module of claim 1, having more openings forming inletchannels than openings forming outlet channels.
 19. The filter module ofclaim 1, wherein the openings in the sheet material for each type ofchannels are arranged in parallel rows.
 20. A filter module comprising abody of wound layers of a sheet material, said body having an innerperipheral surface and an outer peripheral surface, a winding axis and apassage extending along the winding axis of said body and in fluidcommunication with said inner peripheral surface, said sheet materialhaving a plurality of openings formed therein, said openings forming twotypes of channels within the wound layers of sheet material of saidbody, said channels extending in a direction from the inner peripheralsurface to the outer peripheral surface, wherein the openings in thesheet material for each type of channels are arranged in parallel rows,and the openings for one type of channel are arranged in groups of twoor more adjacent rows, and the openings for the other type of channelare arranged in a lesser number of rows, a first type of channels beingopen at one end at said outer peripheral surface of the body and closedat the other end located adjacent to said inner peripheral surface, asecond type of channels being open at one end at said inner peripheralsurface of the body, in fluid communication with said passage and closedat the other end located adjacent to said outer peripheral surface, saidchannels of the one type being separated from the channels of the othertype by portions of sheet material, one of said types of channels beinginlet channels communicating with a fluid inlet of said filter module,the other of said types of channels being outlet channels communicatingwith an outlet of said filter module, wherein the sheet material hasareas at an edge of the openings forming the inlet channels, thethickness of the areas being smaller than the thickness of the sheetmaterial remote from the openings forming the inlet channels.
 21. Afilter module comprising a body of wound layers of a sheet material,said body having an inner peripheral surface and an outer peripheralsurface, a winding axis and a passage extending along the winding axisof said body and in fluid communication with said inner peripheralsurface, said sheet material having a plurality of openings formedtherein, said openings forming two types of channels within the woundlayers of sheet material of said body, said channels extending in adirection from the inner peripheral surface to the outer peripheralsurface, a first type of channels being open at one end at said outerperipheral surface of the body and closed at the other end locatedadjacent to said inner peripheral surface, a second type of channelsbeing open at one end at said inner peripheral surface of the body, influid communication with said passage and closed at the other endlocated adjacent to said outer peripheral surface, said channels of theone type being separated from the channels of the other type by portionsof sheet material, one of said types of channels being inlet channelscommunicating with a fluid inlet of said filter module, the other ofsaid types of channels being outlet channels communicating with anoutlet of said filter module, wherein the openings forming the inletchannels are arranged in a predefined pattern, said pattern beingrepeated multiple times along the winding direction of the sheetmaterial such that the distance between openings of the same kindbelonging to one pattern is different from the distance of adjacentopenings of the same kind belonging to different patterns, and whereinthe sheet material has areas at an edge of the openings forming theinlet channels, the thickness of the areas being smaller than thethickness of the sheet material remote from the openings forming theinlet channels.
 22. The filter module of claim 1, wherein the said sheetmaterial is a depth filter material which is maintained in a compressedstate, such that said body of wound layers constitutes a depth filterunit.
 23. The filter module of claim 22, wherein the compression of thesheet material is such that the thickness of the compiled layers of thebody amounts to 99% or less of the thickness of same number ofindividual layers of sheet material.
 24. The filter module of claim 23,wherein the thickness of the compiled layers of the body amounts toabout 20% to 99% of the thickness of the same number of individuallayers of sheet material.
 25. The filter module of claim 24, wherein thethickness of the compiled layers amounts to about 97% to about 85%. 26.The filter module of claim 1, wherein the innermost and/or the outermostlayers of sheet material are compressed at least to the extent the bodyis compressed.
 27. The filter module of claim 26, wherein the twoinnermost and/or the two outermost layers are compressed to an extentsubstantially corresponding to the degree of compression of the body.28. The filter module of claim 1, wherein the sheet material comprises amatrix including a compressible material and/or a material which swellsin contact with the fluid to be filtered.
 29. The filter module of claim1, wherein the sheet material comprises a matrix incorporating anadditive.
 30. The filter module of claim 29, wherein the additive ispresent in an amount of up to about 70% by weight, based on the weightof the sheet material.
 31. The filter module of claim 29, wherein theadditive comprises an essentially incompressible particulate component,while the matrix of the sheet material includes a compressible materialand/or a material which swells in contact with the fluid to be filtered.32. The filter module of claim 29, wherein the additive comprises aporous particulate additive.
 33. The filter module of claim 29, whereinthe additive comprises a filter aid.
 34. The filter module of claim 29,wherein the additive comprises a treatment agent.
 35. The filter moduleof claim 29, wherein the additive comprises a reactive agent.
 36. Thefilter module of claim 29, wherein the additive comprises an absorptiveor adsorptive agent.
 37. The filter module of claim 29, wherein theadditive is selected from kieselguhr, perlite, bentonite, activatedcarbon, zeolite, micro crystalline cellulose and PVPP.
 38. The filtermodule of claim 1, wherein the sheet material comprises a matrix saidmatrix including an organic polymer material.
 39. The filter module ofclaim 1, wherein the inner peripheral surface of the body is supportedby a hollow support member.
 40. The filter module of claim 1, furthercomprising a precoat, wherein at least one type of channels has achannel surface supporting the precoat.
 41. The filter module of claim4, wherein the flow path created by the areas at the edge of theopenings has a surface supporting the precoat.
 42. The filter module ofclaim 5, wherein the macro-porous strip-like element has a surfacecoated with a precoat.
 43. The filter module of claim 1, wherein saidmodule comprises a clamping means positioned on the outer peripheralsurface of the body, said clamping means maintaining the sheet materialin a compressed state.
 44. The filter module of claim 1, wherein thebody comprises in the vicinity of and spaced apart from its both endfaces, a plurality of outlet channels.
 45. The filter module of claim 1,wherein the openings forming the outlet channels are arranged indisc-like areas of the body, said disc-like areas not comprisingopenings forming inlet channels.
 46. The filter module of claim 1,wherein the sheet material comprises a unitary tape having a first endportion and a second end portion, wherein at least one of the endportions of the tape has a smaller thickness than portions of the tapein between the first and second end portions.
 47. The filter module ofclaim 46, wherein at least one of the first and second end portions ofthe tape has a tapering cross-section in the lengthwise direction of thetape.
 48. The filter module of claim 39, wherein the hollow supportmember provides a closure for the first type of channels at the innerperipheral surface.
 49. The filter module of claim 43, wherein theclamping means provides a closure for the second type of channels at theouter peripheral surface.